1. Field Of The Invention
This invention relates to stud tensioning apparatus and more particularly to apparatus to adapt conventional studs for use with stud tensioners.
2. Description Of The Prior Art
Stud tensioners have long been shown to be an effective and superior means of tightening threaded fasteners on studs. However, heretofore, in order to use stud tensioners it was necessary to have specially designed and sized studs and nuts which would mate with the operative parts of the stud tensioners.
Examples of such stud tensioners are shown in U.S. Pat. No. 3,015,975, issued Jan. 9, 1962, to J. L. Biach, and U.S. Pat. No. 3,106,071, issued Dec. 22, 1964, to J. L. Biach, the entire disclosures of which are incorporated herein by reference.
It was, therefore, not possible to adapt the standard type of stud tensioner to existing threaded nut fastening devices because of the absence of the special shapes and sizes necessary for coaction with the stud tensioner.
Many attempts have been made in the past to transform threaded fasteners for attachment to various systems, but none of the prior art contemplated or taught the means or function by which standard threaded fasteners could be effectively adapted for use with stud tensioners.
Taylor, U.S. Pat. No. 1,086,737, discloses a stay bolt which has a tensioning feature for the spherical head of the bolt. This feature relies however, not on any structure internal to the shaft 5, but rather on the exertion of forces directly on the spherical head.
Guy, U.S. Pat. No. 1,965,412, discloses a threaded exterior nut 21 surrounding a threaded shaft 20. A threaded aperture 24 is formed in the upper portion of the shaft. A threaded member 25 having male threaded portion 28 is inserted into the upper portion of the shaft.
Zetterciuist, U.S. Pat. No. 2,320,398, relates to cooling equipment and apparatus where the bolting of a stud is accomplished at very high temperatures.
Muster, U.S. Pat. No. 2,391,031, shows a nut designed for use with sheet metal. The nut has a plurality of tab portions therein designed for mating with an insert which has a threaded internal aperture.
Leufven, U.S. Pat. No. 2,571,265, has a nut 2 engaging bolt 1. The bolt 1 has an internal threaded aperture therein. The device relies on the action of a fluid in annular chamber 16 which is pressurized so as to modify the mechanical forces exerted by the nut/bolt structure.
May, U.S. Pat. No. 2,736,219, utilizes the spring loaded two piece arrangement shown in FIG. 2 as the bolt tensioner.
Hansen, U.S. Pat. No. 2,770,997, particularly FIG. 6, shows an attachment which fits over bolt 11. The attachment 12 has a threaded aperture at the top thereof. The patented invention, however, relies on differing coefficients of thermal expansion between male and female members in the threaded arrangements shown in the patent.
Hewlett, U.S. Pat. No. 3,327,380, discusses wire "tendons" used in prestressed concrete. These tendons are terminated in a threaded collar 24 which interfits into an adjustment piece 18. FIG. 7 of Hewlett shows male stressing members inserted into the internal aperture connected to the shaft 68 via the threaded collar. As described, element 61 is a "jack" having spider legs 63. Housing 66 is hydraulic. Element 67 is a piston standing between the legs 63. The sleeve on the tendon engages the head 71. The tubular coupler 72 has internal threads engaging the sleeve 69 and external threads mounting a nut 73. Piston 67 of the jack 61 is externally threaded for engagement within coupler 72. A shim 74 is interposed between the nut 73 and the bearing plate 64.
Gulistan, U.S. Pat. No. 3,561,093, discloses a method of securing a sleeve to a work piece. The sleeve is provided with an abutment at one end and inserted into an opening in the workpiece. The abutment is thus brought into a position adjacent the surface of the workpiece. A special gripping member having a second abutment and a shank is extended through the sleeve so the second abutment engages the sleeve and the shank projects beyond the opposite sleeve end. A tension is then applied to the shank to hold the first abutment against the work piece surface while simultaneously the opposite end of the sleeve is bend outwardly to form a flange to secure the sleeve to the workpiece. This special purpose tool and the various modifications shown therein is designed for those fasteners which are utilized with structural elements of little strength. The special purpose tool itself providing the forces and counter forces necessary to bend the fastening flange into position.
Liffick, U.S. Pat. No. 3,960,047, discloses a nut having three different diameter threaded apertures therein so that the same nut can be utilized on two different size bolts. This is an automotive device and is designed to interfit different threads of a wheel bolt.
Kloren, U.S. Pat. No. 4,010,669, puts two rings or washers between the bolt 1 and surface of the workpiece 2. These rings or washers are specially shaped and apertured and also have screws so as to be positioned relative to each other. The screws and rings or washers are an added means of control of the stress applied to the nut, and the exert the force on the bolt.
Abe, U.S. Pat. No. 4,018,132, uses a differential pitch thread on two sections of the bolt. The invention is utilized in the connecting rod of an automotive engine.
Dahl, U.S. Pat. No. 4,035,858, relates to a method of bolt manufacture.
Latham, U.S. Pat. No. 4,075,923, discloses a tensioning apparatus "T" which is placed on the end of stud S with the nut end removed. Tensioning apparatus is rotated causing the piston member to threadedly engage the stud S and be drawn toward the flange F leaving the end of stud S projecting externally. Pressure is applied to chamber 17 through ports 9 causing the piston to move from the position shown in FIG. 1 to the upward position shown in FIG. 2. This movement causes stud S to be tensioned. Once the stud is tensioned, the nut N is placed on the disposed end of the stud manually and threaded until it rests against portion 5 of the tensioner housing. The tensioner remains in place, the pressure removed and the desired tension is achieved. An alternative embodiment is shown in FIG. 3. This embodiment has two housing sections 25 and 26 which divide the housing into two piston areas. The lower piston and the lower housing section define a lower annular chamber 37 and the upper piston defines an upper annular chamber 38. In this embodiment pressure is applied to the two chambers forcing both pistons to move upwards, thereby tensioning the stud at increased force over the singular piston embodiment of FIGS. 1 and 2.